The present invention relates generally to medical devices to be used during cardiovascular, pulmonary, and neurologic procedures where a cardiopulmonary bypass machine is used. More specifically, the present invention incorporates a cardiopulmonary bypass machine and an aortic catheter to provide neurological protection through differential perfusion and suction.
In general, there has been a steady decline in the amount of cardiac morbidity and operative mortality directly associated with cardiopulmonary bypass (CPB) in recent years. Enhanced myocardial protection, more complete coronary revascularization, improved operating technique resulting in enhanced graft patency rates, and better general patient support such as improved cardiac anesthesia and intensive care practices have been cited as some of the primary reasons for better surgical outcomes. Blumenthal J A, et al. xe2x80x9cMethodological Issues in the Assessment of Neuropsychologic Function After Cardiac Surgery,xe2x80x9d Ann Thorac Surg; 59:1345-50 (1995). However, despite the overall decrease in morbidity and mortality, the incidence of neurologic deficit, in the form of, fatal cerebral injury, stroke, retinal microvascular pathology, impaired level of consciousness, seizures, spinal cord injury, peripheral nerve injury and neuropsychologic deficit has increased.
The occurrence of neurologic deficit, after a cardiac procedure, depends upon a number of factors including: the type of operation, the age of the patient population, the prospective versus retrospective nature of the studies, and the sensitivity of the tests performed. Mills, xe2x80x9cRisk Factors for Cerebral Injury and Cardiac Surgery,xe2x80x9d Ann Thorac Surg 1995, 59:1296-1299. Evidence has suggested that the incidence of stroke, the most dramatic form of neurologic deficit approaches 9% in patients greater than 75 years of age. In addition, severe aortic atheroma is a disease strongly linked to stroke and rises sharply with an increase in age. These correlative factors combined with a subsequent change in population demographics have allowed more high-risk patients, most notably the elderly, to be treated by cardiac surgery and unfortunately, with the attendant risk of neurologic deficit. Nevertheless, even though there is a greater risk of neurologic deficit with an increase in age, the inherent complications of cardiac surgery place all age groups, not just the elderly, at risk.
Neuropsychological testing, a means to quantify subtle cognitive changes in patients due to cerebral damage, has shown that as many as two-thirds of patients undergoing CPB demonstrate some type of neuropsychological deficit postoperatively. The affects of neuropsychologic deficit on any single patient are wide ranging and depend upon the patient""s activity level and intellectual pursuits before surgery, however, common disabilities incurred by patients are impaired memory, concentration and hand eye coordination, with a predictably negative impact on life. Rogers A T, Newman S P, Stump D A, Prough D S: Neurologic Effects of Cardiopulmonary Bypass, in Gravlee G P, Davis R F Utley J R: Cardiopulmonary Bypass Principles and Practice. Baltimore: Williams and Wilkins, 1993, pp. 542-576.
In patients undergoing CPB surgery, substantial amounts of clinical data have shown that the primary etiological mechanisms contributing to neurologic and neuropsychologic deficit are cerebral embolization and hypoperfusion. Cerebral embolic infarction occurs when emboli, such as: platelet aggregation, aggregates of fibrin, clusters of microbubbles, boluses of air, and atherosclerotic plaques, are released into the general blood circulation and lodge in the brain. Hypoperfusion, a second theorized culprit, can potentially create cerebral ischemia, which may result in permanent cerebral infarction due to a lack of oxygenated blood flow to the brain.
Transcranial Doppler Ultrasonography (TCD) and Transcarotid Doppler Echocardiography have been used to measure and detect embolic signals, thereby quantifying when in surgical procedures embolic events are most likely to occur. Results have shown that atheromatous plaque can be released into the general blood circulation when there is cannulation of the aorta, manipulation of the heart and ascending aorta, and application or release of the cross-clamp or side biting clamp to the aorta. Furthermore, boluses of air or xe2x80x9csurgical airxe2x80x9d can enter the general blood circulation when there is cannulation of the heart or aorta and removal of the cross clamp, at the site of venous cannulation and when a surgical intervention requires the opening of the cardiac chambers. In addition, some believe that the extracorporeal circuit can be an ongoing source of potential embolic events. For instance, blood born emboli, such as platelet aggregation and fibrin can occur when anticoagulated blood contacts a foreign surface throughout the extracorporeal circuit and microbubbles may be formed within bubble oxygenators and membrane oxygenators in the extracorporeal circuit. Nevertheless, of all the types of emboli and the sources thereof, it is still unclear as to what type of embolic insult is of greatest detriment to the patient: total embolic volume, constitution of emboli, collateral arterial blood supply of the territory affected or the quality of preexisting parenchymal brain function. Barbut et al., xe2x80x9cAortic Atheromatosis and Risks of Cerebral Embolization,xe2x80x9d J Card and Vasc Anesth; Vol 10, No 1: pp 24-30 (1996).
As is evident from the foregoing discussion, emboli can be released in a number of different ways and in a number of different forms. In addition, an increase in perfusion to resolve the problem of hypoperfusion can potentially expose the brain to more embolic debris since more blood flow is going to the cerebral circulation. Alternatively, a reduction in perfusion lowers the overall flow, volume and cycles of blood to the brain, which has the resultant effect of providing less opportunity for emboli to be introduced into the cerebral blood circulation, but may increase the deleterious effects of hypoperfusion.
Therefore, what has been needed and heretofore unavailable is a method and device for reducing cerebral embolism and eliminating hypoperfusion by assuring that adequate blood flow is being supplied to the brain. Substantial strides have been made addressing either embolic insult or hypoperfusion, but not both in the same device. The present invention solves both of these immediate problems, as well as others.
For example, various strategies have been proposed to mitigate the danger of embolic events during CPB surgery. The use of transesophageal echocardiography (TEE) has been used to assess the extent and severity of atherosclerotic plaque, in patients being diagnosed as having aortic atheroma, in order to optimize cannulation sites and minimize the release of plaque into the general blood circulation arising from aortic cannulation. Arterial line filters, bubble traps, air bubble detectors and the wide spread use of membrane oxygenators have reduced the amount of gaseous emboli released into the general blood circulation. Furthermore, rigorous deairing techniques have been shown to help remove xe2x80x9csurgical airxe2x80x9d, and a general awareness that the manipulation of the heart and aorta can potentially create an embolic event has substantially changed surgical techniques to try and limit these maneuvers. However, none of these techniques address hypoperfusion.
Even more recently, patent literature has disclosed devices and methods for reducing the amount of emboli during surgical interventions. Advances have been made which incorporate filters to trap emboli that may be released during CPB surgery. Patents describing these features include: U.S. Pat. Nos. 5,662,671, 5,769,816 and 5,846,260; WO 97/17100, WO 97/42879, WO 98/02084 and commonly owned, copending patent application Ser. No. 09/158,405 filed on Sep. 22, 1998, by Macoviak et al. In addition, WO 98/24377 describes a carotid filter for accomplishing the same general result.
Other related technologies that reduce cerebral insult caused by emboli are intra-aortic shunts and deflectors, which are described in commonly owned, copending patent application Ser. No. 09/212,580 filed on Dec. 14, 1998, and Ser. No. 60/116,836 filed on Jan. 22, 1999 by Macoviak et al. Furthermore, technology has also been developed which incorporates suction to eliminate emboli after release of an external cross clamp. U.S. Pat. No. 5,697,905 to d""Ambrosio discloses a triple lumen intra-aortic balloon catheter which reduces the release of embolized air and particulate matter into the general body circulation, and WO 99/04848 to Maahs discloses an arterial aspiration catheter to be used in a blood vessel. However, none of these techniques address hypoperfusion.
Furthermore, developments in the area of minimally invasive cardiac surgery (MICS) and the use of balloon catheters to address the clinical problems associated with a traditional median sternotomy and the attendant use of a cross clamp to occlude the ascending aorta have been expanded. For example, U.S. Re Pat. No. 35,352 to Peters describes a single balloon catheter for occluding a patient""s ascending aorta and a method for inducing cardioplegic arrest. A perfusion lumen or a contralateral arterial cannula is provided for supplying oxygenated blood during cardiopulmonary bypass. U.S. Pat. No. 5,584,803 to Stevens et al. describes a single balloon catheter for inducing cardioplegic arrest and a system for providing cardiopulmonary support during closed chest cardiac surgery. A coaxial arterial cannula is provided for supplying oxygenated blood during cardiopulmonary bypass. However, the occlusion balloon of these catheters must be very carefully placed in the ascending aorta between the coronary arteries and the brachiocephalic artery, and the position of the catheter must be continuously monitored to avoid complications.
In clinical use, these single balloon catheters have shown a tendency to migrate in the direction of the pressure gradient within the aorta. More specifically, during infusion of cardioplegia, the balloon catheter will tend to migrate downstream due to the higher pressure on the upstream side of the balloon and, when the CPB pump is on, the balloon catheter will tend to migrate upstream into the aortic root due to the higher pressure on the downstream side of the balloon. This migration can be problematic if the balloon migrates far enough to occlude the brachiocephalic artery on the downstream side or the coronary arteries on the upstream side.
Other developments in minimally invasive cardiac surgery include off-pump procedures. For example, U.S. Pat. Nos. 5,888,247 and 5,875,782 describe methods and devices for performing coronary artery bypass grafting on a beating heart. This approach is deemed beneficial in that it eliminates the complications of an external CPB machine, however this technique does not address how to protect the brain when an embolic event does occur.
Still other related technology involves cardiopulmonary support by selective aortic perfusion. U.S. Pat. Nos. 5,308,320, 5,383,854, 5,820,593, 5,906,588 by Peter Safar, S. William Stezoski, and Miroslav Klain describe a balloon catheter for segmenting a patient""s aorta for selective perfusion of different organ systems within the body. Other US patent applications which address the concept of selective aortic perfusion include commonly owned, copending patent application Ser. No. 08/909,293, filed Aug. 11, 1997; and Ser. No. 09/152,589 filed Aug. 11, 1998 to Safar et al.
Furthermore, U.S. Pat. Nos. 5,738,649, 5,827,237, 5,833,671; and commonly owned, copending patent application Ser. No. 09/060,412, filed Apr. 14, 1998 by John A. Macoviak; and Ser. No. 08/665,635, filed Jun. 17, 1996; by John A. Macoviak and Michael Ross; and Ser. No. 60/067,945, filed Dec. 8, 1997, by Bresnahan et al. and Ser. No. 60/084,835, filed Apr. 25, 1997 by Macoviak et al. describe circulatory support systems and methods of use for isolated segmental perfusion. Selective perfusion can be used to prioritize the flow of oxygenated blood or other protective fluids to the various organ systems, with different temperatures, chemical compositions, flow rates and pressures to achieve optimal preservation of all organ systems within the body. These and all other patents and patent applications referred to herein are hereby incorporated by reference.
Although the previous inventions have made significant strides toward improving outcomes related to CPB surgery, there is still need for improvement. Therefore, what has been needed and previously unavailable is a method and apparatus for reducing the release of embolic material into the general blood circulation, while at the same time maintaining appropriate perfusion flow to avoid hypoperfusion and cerebral ischemia. The present invention solves these immediate problems, can be used in conjunction with much of the above-described technology, and solves other problems as well.
In keeping with the foregoing discussion, the present invention provides methods, systems and devices for performing cardiopulmonary bypass (CPB), cardioplegic arrest, suction of fluid from the aorta to remove embolic or other fluid from the general circulation and the selective segmentation of the arterial system to perform differential perfusion eliminating hypoperfusion. Provided is an aortic catheter having a catheter shaft and at least one occlusion member. In a preferred embodiment, a first occlusion member is expandable from the catheter shaft and a second occlusion member is expandable from the catheter shaft and is positioned distal to the first occlusion member. An arch lumen extends at least in part along the length of the catheter shaft and has a proximal opening coupled to a CPB machine and a distal arch opening located between the first occlusion member and the second occlusion member to provide fluid flow therebetween. A corporeal lumen extends at least in part along the length of the catheter shaft and has a proximal opening coupled to a CPB machine and a distal opening downstream of the second occlusion member to provide fluid flow distal to the second occlusion member. A suction lumen extends at least in part along the length of the catheter shaft and has a proximal suction opening coupled to a suction source and a distal suction opening residing in the aortic lumen of a patient.
The aortic catheter as described above may be combined with other devices to create a catheter system which may include a CPB machine, a suction source, various switches and a venous cannula/catheter to perform complete bypass, partial bypass and antegrade or retrograde fluid flow. Furthermore, the system may also be used in a number of different operating modes, including: stopped heart catheter procedures, concurrent surgical interventions and catheter based interventions, sequential surgical interventions, catheter based interventions and as a safety backup or bail out system in beating heart catheter procedures. The system provides cardiopulmonary support for the patient""s circulatory system and prioritized protection for the patient""s cerebral and corporeal circulation.
In one illustrative embodiment, an aortic catheter is provided having two occlusion members mounted on a catheter shaft which are sized and configured to substantially occlude the aorta and enable the selective management and perfusion of the myocardial, cerebral and corporeal circulations. The catheter is introduced through the ascending aorta and is navigated transluminally until the first occlusion member is positioned between the brachiocephalic artery and the coronary arteries and the second occlusion member is positioned downstream of the left subclavian artery. A corporeal lumen has a distal corporeal opening that is sized and configured to provide blood flow downstream of the second occlusion member at a flow rate that is sufficient to sustain appropriate metabolic demands of the corporeal body. An arch lumen has a distal arch opening that is sized and configured to provide blood flow downstream of the first occlusion member at a flow rate that is sufficient to sustain the life preserving metabolic demands of the cerebral circulation. A suction/cardioplegia lumen has a distal suction/cardioplegia opening that is sized and configured to provide cardioplegia, heart arresting fluid or heart therapeutic fluid to the myocardium, as well as provide aspiration of the aortic root upstream of the first occlusion balloon.
In another illustrative embodiment, an aortic catheter is provided having an outer tubular member and an inner tubular member that are arranged in a coaxial relationship. The inner tubular member is slidably disposed within the outer tubular member and is completely removable therefrom or alternatively may be built as an integral assembly that is nevertheless moveable relative to the outer tubular member. When the inner tubular member is completely removed or partially withdrawn, the outer tubular member may be used as an introducer cannula for the insertion of the inner tubular member or any other catheter or medical device. Alternatively, the outer tubular member may be used as a stand alone device in combination with an external cross-clamp, or other occlusion catheter by expanding the first occlusion member to occlude the aorta and having a flow lumen of sufficient size to provide adequate fluid flow to the cerebral and corporeal systems.
A single occlusion member mounted on the inner tubular member is sized and configured to substantially occlude the aorta to enable the selective management and perfusion of the cerebral and corporeal circulations. The catheter is configured for antegrade introduction through the ascending aorta and is navigated transluminally until the occlusion member is downstream of the left subclavian artery. The coaxial design creates an annular space that defines an arch lumen. The arch lumen has a distal arch opening that is sized and configured to provide blood flow upstream of the occlusion member at a flow rate that is sufficient to sustain life preserving metabolic demands of the cerebral circulation. In addition, the arch lumen is configured for aspirating the area downstream of the aortic valve. A corporeal lumen has a distal corporeal opening that is sized and configured to provide blood flow downstream of the occlusion member at a flow rate that is sufficient to sustain the metabolic demands of the corporeal body.
In another embodiment an aortic catheter is provided having two occlusion members mounted on a coaxial catheter shaft. A first occlusion member is mounted on an outer tubular member and a second occlusion member is mounted on an inner tubular member that is slidably disposed within the outer tubular member. The inner tubular member is designed to be completely removed from the outer tubular member or alternatively may be built as an integral assembly that is nevertheless moveable relative to the outer tubular member. When the inner tubular member is completely removed or partially withdrawn, the outer tubular member may be used as an introducer cannula for the insertion of the inner tubular member or any other catheter or medical device. Alternatively, the outer tubular member may be used as a stand alone device with the elimination of the external crossclamp by inflating the occlusion member to occlude the ascending aorta and having a flow lumen of sufficient size to provide adequate fluid flow to the cerebral and corporeal systems.
When used in conjunction with an inner tubular member having a second occlusion member, the inner tubular member is configured to be navigated transluminally until the second occlusion member is positioned downstream of the left subclavian artery so that the cerebral, myocardial and corporeal circulations are isolated. The coaxial configuration of the inner and outer tubular member creates an annular space that defines an arch lumen. The arch lumen has a distal arch port that is sized and configured to provide blood flow downstream of the first occlusion member at a flow rate that is sufficient to sustain life preserving metabolic demands of the arch circulation. A corporeal lumen has a corporeal port that is sized and configured to provide blood flow downstream of the second occlusion member at a flow rate that is sufficient to sustain appropriate metabolic demands of the corporeal body. A suction/cardioplegia lumen extends through the outer tubular member and is in fluid communication with a distal suction/cardioplegia opening that is in fluid communication with the aortic root such that cardioplegia delivery and aspiration of the aortic root is possible upstream of the first occlusion member.
A system for performing CPB is disclosed which incorporates a venous cannula for withdrawing fluids from a vessel into a CPB machine, a left ventricle cannula for venting the left ventricle, a cardiotomy suction cannula for removing blood from the surgical field, and an arterial cannula having two occlusion members configured to segment the aorta and to provide differential perfusion to the cerebral circulation and the corporeal circulation and also to provide for the delivery of cardioplegia and aspiration of the aortic root.
A system for performing CPB is also provided having an aortic cannula/catheter configured for segmenting the aorta into various subsystems, a venous cannula/catheter configured for segmenting the venous system into various subsystems, a coronary sinus catheter, a therapeutic catheter and a switching mechanism. The present system is configured for complete isolation of the myocardial, cerebral and corporeal circulations, for antegrade, retrograde and/or alternating retrograde, antegrade perfusion to the cerebral circulation and antegrade, retrograde and/or alternating antegrade and retrograde cardioplegia delivery to the myocardium. Furthermore the present invention has a fluid instrument lumen configured for cardioplegia delivery, aspiration and for receiving a second therapeutic catheter, drug delivery catheter or fiber-optic catheter. The aortic catheter is configured for retrograde introduction into the patient""s aorta via a peripheral arterial access point, such as the femoral artery. Alternatively, the aortic catheter may be configured for central approach without departing from the scope of the invention.
A venous drainage catheter system is provided that is configured for central introduction or alternatively through the femoral vein or other suitable venous access point in the lower extremities. Alternatively, the dual lumen venous drainage cannula may be configured for introduction though the patient""s superior vena cava via the jugular vein or other suitable venous access point in the neck or upper extremities.
The venous drainage cannula system includes a first occlusion balloon or other expandable occlusion member mounted on a first tubular shaft, which is positioned within the patient""s superior vena cava when in the operative position, and a second occlusion balloon or other expandable occlusion member, mounted on a second tubular shaft, which is positioned within the patient""s inferior vena cava when in the operative position. Alternatively, a single catheter can be used with two occlusion balloons mounted on the catheter shaft. When the venous drainage catheter is configured for femoral artery introduction, the first occlusion balloon is mounted near the distal end of the tubular shaft and the second occlusion balloon is mounted somewhat proximal to the first balloon. Alternatively, for jugular vein introduction, these positions are reversed.
Venous blood from the head and upper extremities enters the patient""s superior vena cava and is drained out through the first venous drainage lumen of the venous drainage catheter as the first occlusion balloon prevents blood from traveling into the right atrium from the superior vena cava. The blood is oxygenated, cooled and recirculated by the first blood circulation system to the head and upper extremities through the arch perfusion lumen of the arterial cannula.
The corporeal loop of the circulatory support system is created by having a venous drainage port in fluid communication with the inferior vena cava drainage lumen. Optionally, vacuum assist may be used to enhance venous drainage through the second venous drainage lumen of the venous drainage cannula. Venous blood from the viscera and lower extremities enters the patient""s inferior vena cava and is drained out through the second venous drainage lumen of the venous drainage cannula. The blood is oxygenated, cooled and recirculated by the second blood circulation system to the viscera and lower extremities through the corporeal perfusion lumen of the arterial catheter.
Alternatively, the venous drainage cannula may be provided with a third venous drainage lumen within the tubular shaft connected to the drainage ports between the first and second balloons for draining the patient""s right atrium and the coronary sinus. A separate coronary perfusion loop can be created by connecting the third venous drainage lumen to the inflow of a third blood circulation pump and connecting the outflow of the pump to the cardioplegia lumen of the arterial cannula. The third blood circulation pump may be a peristaltic roller pump, a centrifugal blood pump or other suitable blood circulation pump. Preferably, the coronary loop also includes a venous blood reservoir, a blood oxygenator and heat exchanger in series with the third blood circulation pump.
As another alternative, the coronary circulation can be isolated by using a coronary sinus catheter for retrograde or antegrade administration of cardioplegia into the patient s coronary arteries with complete isolation of the myocardium. A separate coronary perfusion loop can be created by connecting the coronary sinus lumen to the inflow of a third blood circulation pump and connecting the outflow of the pump to the cardioplegia lumen of the arterial cannula. The third blood circulation pump may be a peristaltic roller pump, a centrifugal blood pump or other suitable blood circulation pump.
Furthermore, the system of the present invention is equipped with a switching mechanism that is used to provide either antegrade flow or retrograde flow, or may be used to alternate between retrograde flow and antegrade flow as the surgical procedure dictates.
Methods are provided which include providing an aortic catheter having a catheter shaft having a distal portion, and a corporeal lumen which extends at least in part along the length of the catheter shaft and opens as at least one distal corporeal opening. An arch lumen extends at least in part along the length of the catheter shaft and opens as at least one distal arch opening. An occlusion member is expandable from the aortic catheter residing between the distal corporeal opening and the distal arch opening. A suction switch, having a first position and a second position is configured for converting the arch lumen to a suction lumen. The distal portion of the aortic catheter is inserted into a patient""s ascending aorta and is navigated transluminally through the aorta until the occlusion member is positioned in the ascending aorta upstream of the brachiocephalic artery. The occlusion member is expanded to resist or to occlude blood flow in the patient""s ascending aorta. Heart arresting material is delivered to the heart of the patient to at least partially arrest the heart and the catheter shaft is navigated until the occlusion member is located in the descending aorta downstream of the left subclavian artery. Blood is perfused at a first temperature upstream from the occlusion member through the arch perfusion lumen and blood is perfused at a second temperature downstream of the occlusion member through the corporeal lumen. The suction switch may be activated at any time during the surgical procedure to evacuate fluid from the aorta.
In addition to the above method, a coronary sinus catheter may be provided to provide retrograde perfusion to the myocardium and a venous cannula may also be provided in conjunction with a switch to enable retrograde delivery to the cerebral circulation while the arterial catheter serves as a means for withdrawing fluid.